VCSEL based Faraday rotation spectroscopy with a modulated and static magnetic field for trace molecular oxygen detection

S. G. So, E. Jeng, Gerard Wysocki

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

Faraday Rotation Spectroscopy (FRS) is a useful technique for quantification of paramagnetic trace gases with significantly higher sensitivity when compared to direct absorption techniques. Our prototype system based on the openPHOTONS sensor core measures the concentration of molecular oxygen (O2) in the A band using a 763-nm vertical cavity surface emitting laser. We provide detailed analysis of two measurement methods based on FRS using the same sensor configuration: one with a modulated magnetic field, and one with a static magnetic field in combination with wavelength modulation. Our spectra signal-to-noise ratios agree well with our simulations via modeling of the FRS signal. For alternating magnetic field, we achieve an equivalent minimum detectable absorption (MDA) of 8.86× 10-7/Hz1/2 resulting in a minimum detection limit of 30 ppmv• m/mathrmHz1/2 of O2, limited by detector noise and laser noise. For the same system configuration in the static field case, parasitic etalon fringes limited the MDA to 4.8\times 10-6/Hz1/2 . In both cases, we describe methods to improve signal-to-noise ratio based on our data and models.

Original languageEnglish (US)
Pages (from-to)279-291
Number of pages13
JournalApplied Physics B: Lasers and Optics
Volume102
Issue number2
DOIs
StatePublished - Feb 1 2011

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)
  • Physics and Astronomy(all)

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